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In this paper we address the processes that produce radio, EUV and HXR radiation in the ICM. First we consider NT Bremsstrahlung as the source of HXRs which, as shown earlier (P01), faces the difficulty of its low yield compared to Coulomb losses. We describe results from a more detailed analysis of the lifetimes of NT electron tails (or bumps) in a hot ICM than that presented in P01, where cold target loss rates were used. We find that the lifetimes of NT tails is increased by a factor of <3 so that the above difficulty becomes less severe but production of HXRs via NT Bremsstrahlung remains problematical. Next we discuss the expected radiative signature of relativistic electrons and show that radio and HXR observations can be explained by synchrotron and IC scattering of CMB photons. But now one requires a low magnetic field which is far from equipartition with the electrons. Finally we give a rough estimate of the gamma-ray signature of the relativistic electrons and point out several possible scenarios in which the gamma-ray fluxes might exceed the GLAST threshold. Based on these results we present an average spectrum of electrons that is required and possible extensions of it into the low energy regime. Production of these spectra is discussed by Petrosian & Bykov 2008 - Chapter 11, this volume.

Acknowledgements The authors thank ISSI (Bern) for support of the team "Non-virialized X-ray components in clusters of galaxies". A.M.B. acknowledges a support from RBRF grant 06-02-16844 and RAS Programs.